Photosensitive heat-resistant materials are useful as an interlayer insulating film and a passivation film of LSI, etc.
Polyimide which is a heat-resistant material is practically in use as an insulating film or a passivation film of LSI and the like because it can be formed into a film more easily than inorganic materials and it is low in dielectric constant and rich in toughness.
Formation of a pattern from polyimide involves a step of coating photoresist and a step of stripping it off, which make the process quite complicated. Further, transfer of a relief pattern via resist is accompanied by a drop in dimensional accuracy. Thus, in order to simplify the step of fine processing and enhance the accuracy thereof, it has been desired to develop a heat-resistant material which can directly be subjected to a fine processing by the use of light.
As for the material for the purpose mentioned above, a variety of materials have so far been proposed in the field of negative tone photosensitive materials. However, since many of the negative tone photosensitive materials use a crosslinking reaction, a swelling of light-exposed portion takes place in a developing solution, which is disadvantageous for the practice of fine processing of high resolution. Further, some processes require to use a positive type photosensitive material. For these reasons, a positive tone photosensitive material has been desired.
Further, from the viewpoint of prevention of environmental pollution and improvement of working environment, a photosensitive resin composition developable with an alkaline aqueous solvent and capable of replacing the prior photosensitive resin compositions using a developing solution of chlorinated solvent type or organic solvent type has been desired.
Positive tone photosensitive heat-resistant materials developable with an alkaline aqueous solvent can be classified into those prepared by introducing photosensitive groups into a polyamic acid through intermediation of covalent bond and those prepared by adding a photosensitive material to a polyamic acid.
As the former, photosensitive nitrobenzyl ester of polyamic acid (JP-B-1-59571) can be referred to. As the latter, the photosensitive heat-resistant material comprising polyamic acid and an orthoquinonediamide-sulfonic ester derivative (JP-A-4-168441, JP-A-4-204738), the photosensitive heat-resistant material comprising a polyamic acid and dihydropyridine derivative (JP-A-6-43648), the photosensitive heat-resistant material comprising polyamic acid and a diazidonaphthoquinonesulfonimide derivative, etc. can be referred to.
From the viewpoint of the kind of polyamic acid applicable and the easiness of preparation of photosensitive resin, those prepared by adding a photosensitive material are considered more advantageous than the other ones.
Polyamic acid has a very high dissolution rate in alkaline developing solution. Accordingly, for making a polyamic acid photosensitive, it is necessary to use a photosensitive material having a high dissolution-inhibiting effect or to lower the dissolution rate of polyamic acid.
Since prior orthoquinonediazides are mainly photosensitive materials for novolak type resist, they hardly exercise a dissolution-inhibiting effect on carboxyl group-containing polymers. Accordingly, in the photosensitive resins using a carboxyl group-containing polymer such as polyamic acid or the like and an orthoquinonediazide, the dissolution-inhibiting effect of unexposed portion and the dissolution-promoting effect of exposed portion are both small, so that sensitivity, resolution and aspect ratio are all insufficient.
Since orthoquinonediazide which is a photosensitive material for novolak type resist hardly exercises a dissolution-inhibiting effect on polyamic acid as mentioned above, polyamic acid/polyamic acid ester copolymer (JP-A-4-204738), polyamic acid ester having carboxyl groups in the diamine parts (JP-A-4-168441), etc. are used for lowering the dissolution rate of polyamic acid. These materials, however, are small in the dissolution-inhibiting effect of the unexposed portion and dissolution-promoting effect of the exposed portion and unsatisfactory in resolution, sensitivity and aspect ratio, so that no sufficient relief pattern can be obtained therefrom.
On the other hand, some of the orthoquinonediazide compounds having urea linkage are referred to as photosensitive materials. As examples thereof, positive tone photosensitive resins comprising a novolak resin (JP-A-4-274431) and positive tone photosensitive resins comprising an acrylic acid resin (JP-A-4-345164) can be referred to. However, these photosensitive resins are low in heat-resistance and not applicable to the passivation film and interlayer insulating film of LSI aimed at in the present invention.
It is an object of the present invention to solve the above-mentioned problems by providing a positive tone photosensitive resin composition high in the dissolution-inhibiting effect of the unexposed portion and dissolution-promoting effect of the exposed portion, excellent in resolution, sensitivity and aspect ratio, capable of giving a satisfactory relief patter and heat-resistance of the thus formed pattern, and suitable for use as passivation film and interlayer insulating film for LSI, and a method for forming a pattern using said composition.
It is another object of the present invention to provide an electronic device obtained by forming a pattern from said positive tone photosensitive resin composition, and a method for production of said device.